I was at the bottom of south mountain in phoenix arizona. watching from ground level my girlfriend noticed a blue orb moving across the horizon. as she pointed it out to me, the orb stopped and disappeared. then re-appeared in the same spot. and continued doing that as it moved across the sky. a few days later i was in the same location with my father working on my car and he spotted another orb, but this one was red he called me over to see it. as we watched it hovering for about 30 seconds, it made a violent turn to the east slightly descending. at that exact moment it either turned into a green orb or it split into 2 orbs red & green. hard to tell, happened very quick. then a few moments later, a loud "boom" like a cannon.. made us jump and continued throughout the night every 15 minutes or so. no media coverage of these loud "booms" and they shook the ground we stood on. however not as bad as a sonic boom. a little more subtle.